Are you sure that it's not just a US plug but a universal (i.e. 100-240V, 50-60Hz) power supply? If it is a universal power supply but the wrong plug then you can either use a travel adaptor or snip the plug off and wire on an Irish one. If it is a US only (120V/60Hz) power supply then you will either need a step down transformer (to convert the Irish 220V supply to 120V) or an alternative power supply that gives the approporiate DC output and polarity (usually positive centre, negative outside). What DC rating is noted on the actual charger device and what polarity is outlined? It may be that a multi-voltage transformer from Argos or the like might do. Make sure that you get one of the correct mA rating (e.g. they can come in 800mA, 900mA, 1500mA, 2400mA, 3000mA etc.).